There have conventionally been provided packaging machines which support a packaging bag in a suspending manner with an upper open end thereof up, fill the packaging bag with rice, sugar, salt, pet food or the like and apply heat seal to an upper open end of the bag, thereby packaging a powder or granular article.
However, when the packaging bag is sealed with air remaining in the bag, compressed remaining air sometimes damages or collapses the packaging bag during storage of packaging bags in a piled state or transportation of packaging bags.
Accordingly, a process has been employed in which a packaging bag filled with an article and sealed is shaped on a shaping conveyor attached to the packaging machine, into a substantially predetermined thickness and a small aperture is formed in the bag using a needle so that remaining air is eliminated. Another process has been employed in which the packaging bag is heat-sealed in a pattern of labyrinth so that the bag has an air permeability or a vent filter is provided together with the heat seal in the labyrinth pattern so that remaining air is eliminated.
However, when the packaging bag has the small aperture or a vent portion, foreign matter such as insects is entrapped into the packaging bag. In view of this, the applicant previously proposed a packaging method which is capable of packaging with an imperforate bag provided with no small apertures or no aerating part, preventing contamination of foreign substances such as insects and further preventing the packaging bags from being damaged or collapsed during storage in a piled state or transportation (JP-A-2010-126244).